add fix for 'No Such Window' error

reason:
from 6.4 secotion in http://www.w3.org/TR/webdriver/, it says:
Once the window has closed, future commands must return a status code of
no such window until a new window is selected for receiving commands.
how to fix:
1. let close_window() automaticly switches to prevoius window;
2. capture NoSuchWindowException when select_window() /
_select_matching()/get_current_window_handle()

Author: divfor

src/Selenium2Library/keywords/_browsermanagement.py

@@ -212,8 +212,15 @@ def switch_browser(self, index_or_alias):
     # Public, window management
 
     def close_window(self):
-        """Closes currently opened pop-up window."""
+        """Closes currently opened pop-up window and switch back to previous window.
+        It assumes the last opened window is in the last index of window list.
+        However, as opened windows are list-returned from tree-order in remote end,
+        please use 'Select Window' if automatic switching does not work as expected.
+        """
         self._current_browser().close()
+        handles = self._current_browser().get_window_handles()
+        if len(handles) >= 1:
+            self._current_browser().switch_to_window(handles[-1])
 
     def get_window_identifiers(self):
         """Returns and logs id attributes of all windows known to the browser."""

src/Selenium2Library/locators/windowmanager.py

@@ -95,10 +95,13 @@ def _get_window_infos(self, browser):
         return window_infos
 
     def _select_matching(self, browser, matcher, error):
-        starting_handle = browser.get_current_window_handle()
+        try:
+            starting_handle = browser.get_current_window_handle()
+        except NoSuchWindowException: pass
         for handle in browser.get_window_handles():
             browser.switch_to_window(handle)
             if matcher(browser.get_current_window_info()):
                 return
-        browser.switch_to_window(starting_handle)
+        if starting_handle:
+            browser.switch_to_window(starting_handle)
         raise ValueError(error)